Vapor detector



P 1947- v k. T. MARETTE ET AL 2,427,291

VAPOR DETECTOR Filed NOV. 14, 1945 amie? Patented Sept. 9, 1947 VAPOR DETECTOR Ralph T. Marette and Wilbur .R. Richards, Cleveland, Ohio, assignors to The Arc Equipment Ohio, a corporation of Corporation, Bryan,

Ohio

ApplicationNovember 14,1945, Serial No. 628,524

6 Claims. 1

This invention has to do with a vapor detector of the type wherein a pair of electrodes is designed to have a chemical film applied thereto, the film being subjected to a flowing gas to be tested, and the electrical resistance of the film changing in accordance with the water vapor content of the flowing gas.

One object of the invention is to provide a vapor detector wherein the electrodes are supported in spaced relation to each other and insulated from each other in a novel manner, the support for the two being in the form of fused glass between a tubular stainless steel electrode and a stainless steel wire electrode, thus providing a. gas tight bond between the electrodes which will withstand high operating pressures.

Another object is to provide a vapor detector having a plug body for mounting it in a vapor testing cell block or the like, so that the detector can be readily removed therefrom for renewing the chemical film on the electrodes, the plug body having a portion protecting the electrodes against injury.

Still another object is to provide a vapor de tector plug which has parts assembled in a novel manner permitting effective insulation of one of the electrodes from the plug body itself, and at the same time sealing both electrodes against any leakage of gas outwardly between the insulating material and the two electrodes.

A further object is to provid a tapered plug arranged to serve as one of the electrodes, the plug having a bore therethrough with the other electrode mounted in the bore and spaced from the first electrode by glass or the like fused to both electrodes, the tapered character of the plug effecting a gas tight connection with the plug body, and the direction of the taper being such that high pressure within the cell blocks tends to tighten the plug in the body.

Stil a further object is to provide an electrode construction for a vapor detector which mounts a pair of electrodes closely adjacent each other, with insulating material of quartz or glass fused to both electrodes, and the surfaces of the electrodes and the glass being subsequently round off to a plane surface to which a chemical film can be applied for vapor detection purposes.

With these and other objects in view, our invention consistsin the construction, arrangement ill and combination of the various parts of our device whereby the objects contemplated are attained, as hereinafter more fully set forth, pointed out in our claims and illustrated in the accompanying drawings, wherein:

Figure 1 is anelevation of a vapor'detector embodying our invention and showing it about double size, although size is .immaterial.

Fig. 2 is a partial sectional view of the vapor detector showing it mounted in a cell block, the block being shown in section.

Fig. 3 is an enlarged sectional View on the line 3-3 on Fig: 2. showing an end view of the inner end of the detector, and

Fig. 4 is an enlarged sectional view showing the two electrodes as asub-assembly of the detector.

On the accompanying drawing we have used the reference character P to indicate a plug body which has a threaded portion I2 adapted to thread into an-opening In of a cell block-C or the like. The plug body P has a tapered seat I4 adapted to coact with a similarly tapered seat IS in the cell block to provide a gas tight joint which will withstand extremely high pressures within the cell block when the plug body P is screwed into the block.

The plug body P also has a threaded portion lr8'onto which a connector 20 of an electric cable 22 may be .remova'bly screwed. The cable 22 has a pair of wires 24 and 26, the wire 24 extending to a contact 21, and the wire v2'5 being grounded to the connector 20 so that when the connector is screwed onto the plug body ther will be a grounded connection therewith.

The plug body .1? has a bore comprising a tapered portion 28 and two other portions 30 and 32 as best illustrated in Fig. 2. Seated in the tapered bore portion 28 of the bore is a tapered plug .34, the plug being formed preferably of stainless steel, and preferably cemented in position in the tapered bore.

The tapered plug .34 .has a stepped bore 38 through which, and spaced from which, is acentral electrode 38, preferably formed of stainless steel. The electrode 38 is insulated from the plug 34 by insulating material of quartz or glass which isfused to the surface of the wire 38 and to the surface of the bore 36 for the purpose of providing a gas tight insulated seal between .the electrodes.

The electrode 38 is soldered into an eyelet; 42, the solder being shown at 44. The solder 44 makes contact with the terminal 21, and thereby with the wire 24. The eyelet 42 is mounted in an insulated washer 46 which is retained against a shoulder 48 of the plug body by a spun-over portion 50 thereof.

The tapered plug 34 serves as an annular electrode surrounding the electrode 38 and the two may be originally longer than shown by solid lines in Fig. 4, this being illustrated by dotted lines. The glass insulation 40, it will be noted, is also shown dotted as originally extending further to the right in Fig. 4, and these elements present a rough unfinished surface. After the glass has been fused to the electrodes, this surface is ground down to a plane surface indicated by the solid line 52 in Fig. 4. The ground surface is polished smooth to accommodate the acid film on the ground glass which extends from the inner electrode 38 to the outer electrode 34.

By fusing the insulation 40 to both electrodes, a true gas tight joint is made between the in sulation and the electrodes, and this is an important feature of our present invention.

As to the use of the vapor detector, it may be generally stated that a thin film of chemical, such as phosphoric acid, deposited on the face 52 of the detector, has the property of quickly changing in electrical resistance with changes of the water content of many gases with which it is in contact. Thus the wires 24 and 26 may be part of an electric circuit including a galvanometer or other suitable apparatus, and the resistance of the chemical film measured in order to determine the water vapor content of atmosphere or gas in contact with the face 52.

The detector is particularly useful in connection with determining the water vapor content of oxygen for aviators flying at high altitudes, the determination being made at sea level. Too much moisture content in the oxygen results in freezing of droplets of the moisture, which restrict the metering orifices of oxygen systems, sometimes blocking the passages, and depositing on working parts and freezing thereon, which prevents proper functioning of the oxygen system. The maximum allowable water content which has been established by the U. S. Army Air Forces is 0.02 milligram of water per liter of oxygen. This is a relatively minute quantity of water vapor and is not easily measured by those methods which involve dew point determinations. By the chemical film method, a sample of gas of known Water content per unit volume (saturated at controlled temperature and pressure) may be passed over the chemical film, and the film will assume a certain resistance which can be recorded. If a second sample of gas of unknown water content is then passed over the film the resistance will usually be changed, but may be restored to its original value by compressing or expanding the second sample until it contains the same quantity of water per unit volume as the first sample. When this condition is reached the pressure can be noted and the water content of the second sample, in relation to the first, computed.

Since the pressure sometimes required to get the same reading on the second sample as the first sample may go as high as three thousand pounds, it is imperative that an electrode assembly be provided wherein, there is no possibility of the insulation around the electrodes breaking down and permitting mechanical or electrical leakage. This is accomplished in our device by actually fusing the glass 40 to the surface of the electrode 38, and to the inner surface of the bore 36 of the electrode 34. For this purpose acid resisting glass frit has been found satisfactory where the frit is ground fine. A commercial product for this purpose is Glascote Company's #258 acid resisting glass frit. Stainless steel has thus far been found to be the best material suited both to the acid film and the glass frit used, although other metals are more or less satisfactory.

Our arrangement is such that the vapor detector is readily removable from the cell block when it is necessary to renew the chemical film. The film gradually is rendered unusable and it is, therefore, usually necessary to renew it after a number of tests. This is conveniently done by unscrewing the cable connection 20 and then unscrewing the plug body P from the cell block. When the plug body is removed, the electrodes are adequately protected against mechanical injury by a sleeve-like extension 54 on the plug body which surrounds the inner ends of the electrodes.

Some changes may be made in the construction and arrangement of the parts of our device without departing from the real spirit and purpose of our invention, and it is our intention to cover by our claims any modified forms of structure or use of mechanical equivalents which may be reasonably included within their scope.

We claim as our invention:

1. In a vapor detector, a plug bod having a bore therethrough and adapted to be screwed into a cell block or the like, a portion of said bore being tapered, a plug in said bore with the small end of the tapered plug disposed outwardly relative to the cell block, an electrode in said plug body extending through said tapered plug said electrode being sealed and insulated relative to said tapered plug by means of a glass sleeve fused to both the tapered plug and the electrode, said tapered plug constituting a, second electrode and the inner ends of said electrodes and the glass being ground to a plane surface and exposed to the media containing the vapor to be detected,

2. A vapor detector comprising a plug body having a bore therethrough, a portion of said bore being tapered, a plug in said bore, an electrode in said plug body extending through and spaced from said bore, a glass sleeve fused to both the tapered plug bore and the electrode, and spanning the space between them, said tapered plug constituting a second electrode, a portion of both said first and second electrodes being exposed to the media containing the vapor to be detected.

3. A vapor detector of the character disclosed comprising a plug body having a bore therethrough adapted to be screwed into the cell block or the like, a portion of said bore being tapered, a tapered plug cemented in said bore with the small end of the plug disposed outwardly relative to the cell block, an electrode extending through said bore of said tapered plug and spaced therefrom, said electrode and said plug being formed of stainless steel and having a portion thereof exposed to the media containing the vapor to be detected, and acid resisting glass frit fused to said electrode and said tapered plug.

4. A vapor detector comprising a plug body adapted to be screwed into an opening of a pressure container, a plug in said body, an electrical conductor in said body extending through said plug and sealed in relation thereto, the seal being formed of insulatin material fused to both the plug and the electrode, said plug and electrode and the insulation being finished to a plane sur- 5 face and being exposed to the media containing the vapor to be detected.

5. A vapor detector comprising a pair of electrodes, one comprising a sleeve and the other centered in said sleeve, with the electrodes in closely spaced. relation, insulation of fused glass between said electrodes and providing a pressure seal between them, said insulation and said electrodes terminating in a plane surface to which a chemical film is applied, said plane surface being exposed to the media containing the vapor to be detected, and a plug body for supportin said electrodes.

6. A vapor detector comprising a pair of electrodes, one comprising a sleeve and the other centered in said sleeve, a sleeve of glass between said electrodes and fused to them to provide a pressure seal, said insulation supporting the in REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 15 Number Name Date 903,090 Hopkins Nov. 3, 1908 2,078,776 Ruggles Apr. 27, 1937 

